| 摘要 |
A method for cleaning contaminated surfaces, especially semiconductor wafers, using energetic cluster beams is disclosed. In this system, charged beams consisting of microdroplets or clusters having a prescribed composition, velocity, energy and size are directed onto a target substrate dislodging contaminant material. The charged, high energy cluster beams are formed by electrostatically atomizing a conductive fluid fed pneumatically to the tip of one or more capillary-like emitters. The high extraction field necessary for atomization and formation of charged clusters, on the order 105 volts/cm or greater, is provided by applying a potential difference between the emitters and a counterelectrode. Since the charged clusters, typically 0.01 to 0.1 micron in diameter, are multiply charged, acceleration through 10 kV or more results in large substrate impact energies greater than 0.5 million electronvolts. Because beam clusters are massive compared to ion beams, they expend their energy over an extended area of the target causing the simultaneous liftoff and removal of micron and submicron particulates, organic films and metallic contaminants. Although individual cluster impact energies are high, the energy is shared by the large number of cluster nucleons. This results in specific energies at impact less than 1 eV/nucleon, well below material sputtering thresholds, preventing direct etching or damage to impacted surfaces during the contaminant removal process. To prevent substrate charging, neutralization can be accomplished by injecting electrons into focused or nonfocused cluster beams.
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